1. Field of the Invention
This invention relates to an interaxle differential comprising a liquid friction coupling and a planetary gear train comprising three torque-transmitting elements.
2. Description of the Prior Art
British Patent Specification No. 1,357,106 describes an interaxle differential which is of the kind described above. But in that differential the liquid friction coupling serves only to lock the interaxle differential under certain operating conditions.
Published German Application No. 26 36 741 describes a liquid friction coupling which has a liquidcontaining housing and a coupling shaft which protrudes into said housing. Radially inwardly extending, axially spaced apart outer blades are mounted on the housing. Radially outwardly extending, axially spaced apart inner blades are mounted on the shaft and interdigitate with the adjustable blades. The outer blades are movable in a radial plane to vary the overlap between the outer and inner blades. In the known coupling the outer blades constitute a plurality of sets of axially spaced apart blades and the blades of each set are fixed to a mounting shaft, which is rotatably mounted in the housing and parallel to the coupling shaft. The torque which is being transmitted by said known liquid friction coupling will depend on the radial overlap between the outer and inner blades and said radial overlap will depend on the force exerted on the outer blades by springs which act on the mounting shaft in a sense to urge said outer blades radially inwardly and on the centrifugal force which acts on the outer blades during a rotation of the housing and tends to move the outer blades radially outwardly. A ring is provided for adjusting the bias of the springs and said ring cannot be used to move the outer blades radially outwardly and cannot be adjusted at all when the housing is rotating. Besides, during a rotation of the housing when the coupling is in operation the outer blades will be pivotally moved by centrifugal force, regardless of the sense of rotation.